Separation of gaseous mixtures



Oct. 12 1926.

J. LE ROUGE SEPARATION OF GASE OUS MIXTURES Filed Nov. 10, 1923 BY I 52;M v M 44 ATTORNEYS Patented Oct. 12, 1926.

UNITEDSTATES PATENT OFFICE.

' man 'LE noueE, 0E nc "JLOGNE, FRANCE, assrenoa ro socrE'rE LAIRLroUrnE (SOOIE'IE ANONYHE roUE LETUDE ET LEXILOITATION nEs raocEnEseEoaeEs creams), 0E rams, FRANCE.

SEPARATION OE GASEOUS MIXTURES.

Application and November 10, ms, Serial No. 673.929, at in France March10, 1923.

This invention relates to the separation of the constituents of gaseousmixtures by liquefaction and rectification, and articularly toimprovements whereby the e cienc of such separation is materiallyincrease In Letters Patent of the United States, No. 981,748, a methodis disclosed in which a compressed gaseous mixture is subjectedto'lieat-inte'rchange with the gaseous products of the se aration and apart thereof is expanded wit the production of external work and thenliquefied and separated in a rectification column while the remainder isliquefied at its initial pressure by heat-interchange with cold roductsof the se aration in which the liquid portion is uti ized.

' In this process the initial pressure of all uniform, the S0 parts ofthe entering gaseous mixture is pressure being selected so that theexpansion of a part of the gaseous mixture w1t-h external work producesrefrigeration which just sufiices to compensate for losses of coldinqthe operation.

It is the object of the present-invention to increase the eflicienc ofliquefaction processes and particular yto modify and improve the processdescribed in said Letters Patent.

Further ob'ects and advantages of the in vention will e apparent'as itis better understood by reference to the following s ecification andaccompanying drawing w ich illustrates diagrammatically a form ofapparatus adapted to the accomplishment of the present pu use. It is tobe understood that details'of t e apparatus which are well understood bythosev skilled in the art-have been omitted from the drawing and thatother details, articularly with reference to the rectification, may bevaried without departing from the invention or sacrificing 'theadvantages thereof.

. The present invention deperids upon the initial compression of aportion of the gaseous mixture entering t e system to a materiallyhigher pressure than that to which the remaining portion is subjected.This portion of the gaseous mixture at high pressure is caused to travelthrough a temperature exchanger wherein it is subjected to ivered to asuitable expansion device such as an engine or turbine and expanded withexternal work to a relatively low pressure corres onding substantiallyto the pressure at whlch rectification is subsequently conducted. Thecold expanded mixture from the engine or turbine is delivered to aliquefier wherein it is sub'ected to'heat-interchange with a body 0liquid resulting from the rectification. 'Heat-interchan e between thegaseous mixture and the iquid results in liquefaction of the former andevaporation of the latter, and the liquid formed is preferably augmentedby theliquid previously produced from the high' pressure portion of theentering gaseous mixturewhich is delivered under the control of a valveto the liquefier.

The combined liquids are then subjected to rectification in any suitablemanner, for example, by causing them to descend through a column inwhich the are subjected to vapors resulting from t e va rization. ofliquid at the bottom of the co umn. Rectification results in theseparation of the constituents of the liquid, the more volatileconstituents accumulating in the risin vapors while the less volatileare retaine descending liquid. In the case of air the rectificationresults in the reduction of a body of liquid which is $11 stantiallypure The mingled in the oxygen at the bottom of the column. The

-ly cold, are utilize operation while the-balance rises as a rectifyingagent through the column. The other product is nitrogen containing moreor less oxygen which is withdrawn from the top of the column. Bothroducts, being extremed by heat-interchange to cool the incoming gaseousmixture.

'The process may be modified by eliminating the expansion valve throughwhich the gaseous mixture at high pressure passes after initial cooling.Instead of utilizing such a valve that part of the gaseous mixture whichis not liquefied by the prelimina cooling may be caused to pass througha suitable expansion device such as an engine or turbine wherein it issub'ected to expansion with external work. may be delivered then totheliquefier with the expanded rtion of' the mixture which has beenpreviously compressed to a comparatively low pressure.

Referring to the drawing and applying the invention particularly to thetreatment of air, a portion of the air is compressed to a comparativelylow pressure, ten atmos- Q 'heres -for 'exam le and enters an exchangerB at A. It circulates in the exchanger countercurrent to separatedoxygen and nitrogen traveling through the tubes B of the exchanger. Thecompressed air after cooling leaves the exchanger through a pipe C andis delivered to an expander D wherein it is expanded with external work.The cold expanded mixture is delivered through it a pipe M to a coil -Min thebottom of a column N wherein it is subjected to the cooling effectof a body of liquid oxygen accumulated in the bottom of the column.

7 The other portion of the air,for example, one-sixth of the total airtreated, is com- .pressed to ahigh pressure, two hundred atmospheres,for example, and enters a temperature exchanger F through a pipe E. In

-passing through the tubes F of the exchanger the air is subjected toheat-interchange with a cold product of the rectification such as theefiiuent nitrogen delivered from the top of the column through a pipe X.The liquefied portion of the gaseous mixture eventually with a part ofthe'gaseous mixture under high pressure is delivered through anexpansion valve G to a reservoir H under a pressure which is the same asthat of the first portion of air and the liquid separates from the gasin the reservoir H. This latter gas is delivered through a pipe I to thepipe C wherein it joins the low pressure gaseous mixture and isdelivered to the expander D. The liquid from the reservoir H isdelivered through a-valve L to the pi e MT leading to thecoilM, where itjoins t e cold expanded gases from the expander D.

The-liquid formed in and delivered to the 0011 M is transferred throu hcontrolled by a l gfo' wq, zthe e cold expanded mixture liquid in thebottom of the column is dea pipe 0 column N and flows downwardly thereinover a plurality of trays N of the usual 1 .form" employed inrectification columns.

tion and separation of nitrogen from the liquid which descends to thebottom of the column as substantially pure oxygn. The nitro en ormixture of nitrogen and oxygen forming the efiluent from the columnescapes through t e pipe X to the exchanger F. After passing. throughthe exchanger 2. portion of the efliuent escapes through the outlet andthe remainder is delivered through a pipe R tothe exchanger B where itserves to cool the incoming gaseous mixture. Thev gaseous oxygenproduced by vaporization of livered through a pipe T to another sectionof the exchanger B. The efliuent nitrogen escapes from the exchanger Bthrough an. outlets and the oxygen escapes through an outlet U. y

An advantage of the process as described results from the possibility ofcompressing the major portion of the gaseous mixture to a relatively lowpressure. Onlyso much of the gaseousmixture is compressed to a highpressure as is necessary to supply an amount of liquid equivalent to thelosses which inevitably occur in the system. The invention isparticularly desirable in connection with large installments adapted tohandle great no volumes of gases.

I claim I 1. The process of-separating the constituents of gaseousmixtures by liquefaction and rectification, which comprises initiallycompressing a portion of the total volume of the 105 mixture to betreated to a high pressure, partially expanding this portion, compressmgthe balance of the gaseous mixture to a lower pressure, expanding thisportion with external work, combining both portions under conditionseffecting liquefaction thereof and subjecting the liquid formed torectification.

2. The process of separating the constituents of gaseous mixtures byliquefaction and rectification, which comprises initially coma pressingthe gaseous mixture to a high pressure, expanding the mixture, bythrottling to an intermediate pressure, whereby it is partiallyliquefied, expanding the unliquefied 12 residue with external work,subjecting the expanded residue to conditions effecting li uefactionthereof. combining this liquid with the liqfiiid producedby throttlingand :pbjecting t e combined liquids to rectificaion.

3. The process of separating the constituents ofgaseous mixtures byliquefaction and rectification, which comprises initially compressing aportion of the total volume of the 1% sure, partially expandin gaseousmixture to be treated, compressing the balance of the gaseous mixture toa. higher pressure, expanding the highly compressed portion to thepressure of the other portion, expanding both portions with externalwork, liquefying the expanded gaseous tion of aseous mixtures, employinwith production 0 mixture and subjecting the liquid to rectification.

5. The process of separating the constituents of gaseous mixtures by'liquefaction and rectification, which comprises initially compressing aportion of the gaseous mixture to be treated to a high pressure,expanding this portion by throttling to an intermediate pressure,separating the liquid formed from the gaseous portion, compressing thebalance of the gaseous mixture to substantially the intermediatepressure, combining theunliquefied residue with this compressed balanceof the gaseous mixture, ex-

panding the combined gases with external work, liquefying the expandedgases and rectifying the liquid formed with the liquid above separated.

6. Improvements in processes of separaexpan- SIOIl wit separated gas orgases upon leaving the separation apparatus proper cool down a part ofthe gaseous mixture to be treated in order to liquefy it totally orpartially, consisting in compressing this'latter part of the gaseousmixture to a pressure higher than that of the other part, then expandingby simple throttling the liquid thus produced with eventually a part ofthe gas, to a pressure intermediate between the very high pressure'andthe pressure of the separation apparatus proper; then expanding externalwork the gaseous part resultin from the preceding expansion, and thenliquefying and separating this gaseous part in the separation'apparat-usproper. p v i 7 A mode of operation according to claim 6, consisting inthat the intermediate expansion of that part of the gaseous mixturewhich. is at very high pressure takes place at the initial pressure ofthe other part of the gaseous mixture treated;

8. A mode of operation of the process, according to claim 7, consistingin mixing external work and in w ich the the gaseous part resulting fromthe expansion to intermediate pressure with the other part of the othergaseous mixture treated as the latter leaves the exchangers and thenexpanding together these two gaseousjparts with production of externalwork.

9. In the application of the process, according to claim 6, to theseparation of air, a mode of operating consisting in causing thenitrogen leaving the rectification column to cool down, first the aircompressed to the highest pressure and then delivering a part only ofthis nitrogen, thus partially reheated into the exchanger carrying thepart of the air at lower pressure.

- 10. Improvements in processes of separation of gaseous mixtures emloying expansion with external work an in which the separated gas orgases upon leaving the separation apparatus proper cool down a part ofthe gaseous mixture to be treated in order to liquefy it partially,consisting in compressing this latter part of the gaseous mixture to apressure higher than that of the other part, then expanding withproduction of external work the gaseous part resulting from the partialliquefaction and then liquefying and separating this gaseous part in theseparation apparatus proper.

11. The process of separating the constituents of gaseous mixtures byliquefaction and rectification, which comprises initially compressing aportion of the total volume of the mixtureto be treated to a highpressure, cooling this portion, separating the liquid formed from thegaseous portion, partially expanding this gaseous portion with externalwork, compressing the balance of the gaseous mixture to a lower ressure,cooling and partially expanding t is ortion with external work, subjectm'bot expanded gaseous portions to li 'ue action and rectification andusing the a ove separated liquid for this rectification.

12. The process of separating the constituents of gaseous mixtures byliquefaction and.

rectification, which com rises initially compressing a portion of t etotal volume of themixture to be treated to a high ressure, cooling andpartially expanding t is portion by throttling, separating the liquidformed from the gaseous portion, partially expanding this gaseousportion-with external work, compressing the balance of the gaseousmixture to a lower pressure, cooling and partially expanding thisportion with external work, subjecting both expanded aseous portions toliquefaction and recti cation and using the above separated liquidforthis rectification.

13. The process of separatin the constituents of gaseous mixtures byhquefaction and rectification, which comprises initially compressing athe mixture to treated to a high pressure,

rtion of the'totalvolume of cooling and partially expandingthis portionby throttling to an intermedlate pressure, separating the liquid formedfrom the aseous portion, compressing the balance 0 the gaseous mixtureto the intermediate pressure, cooling it, partially expanding it withthe above separated gaseous portion with eous portions to liquefactionand reoti 'tion and using the above separated liquid 10 for thisrectification. I

In testimony whereof I affiri my signature.

JEAN LE RoUE.

